Qos Trust - Cisco Catalyst 4500 Series Command Reference Manual

Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches

qos trust

To set the trusted state of an interface (for example, whether the packets arriving at an interface are
trusted to carry the correct CoS, ToS, and DSCP classifications), use the qos trust command. To set an
interface to the untrusted state, use the no form of this command.
Syntax Description
cos
device cisco-phone
dscp
extend
cos priority
Defaults The default settings are as follows:
•
•
•
Command Modes
Interface configuration mode
Command History Release
12.1(8a)EW
12.1(11)EW
12.1(19)EW
Usage Guidelines
This command is not supported on the Supervisor Engine 6-E and Catalyst 4900M chassis.
You can only configure the trusted state on physical LAN interfaces.
By default, the trust state of an interface when QoS is enabled is untrusted; when QoS is disabled on the
interface, the trust state is reset to trust DSCP.
When the interface trust state is qos trust cos, the transmit CoS is always the incoming packet CoS (or
the default CoS for the interface, if the packet is not tagged).
When the interface trust state is not qos trust dscp, the security and QoS ACL classification will always
use the interface DSCP and not the incoming packet DSCP.
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qos trust {cos | device cisco-phone | dscp | extend [cos priority]}
no qos trust {cos | device cisco-phone | dscp | extend [cos priority]}
Specifies that the CoS bits in incoming frames are trusted and derives the
internal DSCP value from the CoS bits.
Specifies the Cisco IP phone as the trust device for a port.
Specifies that the ToS bits in the incoming packets contain a DSCP value.
Specifies to extend the trust to Port VLAN ID (PVID) packets coming from
the PC.
(Optional) Specifies that the CoS priority value is set to PVID packets; valid
values are from 0 to 7.
If global QoS is enabled, trust is disabled on the port.
If global QoS is disabled, trust DSCP is enabled on the port.
The CoS priority level is 0.
Modification
Support for this command was introduced on the Catalyst 4500 series switch.
Support for extending trust for voice was added.
Support for trust device Cisco IP phone was added.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.4.0SG and IOS 15.1(2)SG)
qos trust
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